Question

Describe double circulation of blood in human beings. Why is it necessary?​

Answer 1

The human circulatory system is a double circulatory system. It has two separate circuits and blood passes through the heart twice. It consists of pulmonary and systemic circulation.

Pulmonary Circulation:
$\bullet$ Lungs are involved in this type of circulation.
$\bullet$ In this pathway, deoxygenated blood from heart is transferred to the lungs through pulmonary artery for oxygenation.
$\bullet$ After oxygenation, blood is carried by pulmonary vein to the left atrium.

Systemic Circulation:
$\bullet$ All systemic organs and tissues are involved in this type of circulation.
$\bullet$ Oxygenated blood goes to tissues and organs through aorta.
$\bullet$ The deoxygenated blood from all parts of body is carried by vena cava to right atrium and then further into the right ventricle.

Need for double circulation:

Double circulation is important as the division of the heart into different chambers prevents the mixing of oxygenated and deoxygenated blood. This improves the efficiency of oxygen transport. This is useful in animals that have high energy needs, like birds and mammals, which constantly use energy to maintain their body temperature.